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gbm: Version the GBM backend interface

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Define a version number for the interface GBM uses
to offload work to its backends/drivers. Store the
version in the backend interface structs provided
to the loader by backends, as well as in the core
interface struct provided to backends by the GBM
loader code to backends.

The backend can create structures of any version
it supports, which can be greater or less than the
interface version specified by GBM in the core
interface structure. Hence, GBM will need to take
care to check the backend version before accessing
any members added to structs defined in
gbm_backend_abi.h after this change.

Similarly, the backend may need to check the
interface version supported by the GBM library
before passing back data in any structure members
that require the GBM library to interact with
them for correct operation. For example, if for
some reason a structure defined in
gbm_backend_abi.h gained a field which was a
pointer to memory allocated by the backend and
freed by GBM, the backend should avoid allocating
this memory if the GBM library did not specify an
interface version new enough to indicate that it
was aware of the new structure member.

Signed-off-by: James Jones <jajones@nvidia.com>
Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9902>
This commit is contained in:
James Jones
2019-10-16 22:16:53 -07:00
committed by Marge Bot
parent 496ea1715e
commit 5baa36f423
6 changed files with 306 additions and 142 deletions
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12
src/gbm/main/backend.c
View File

@@ -30,10 +30,12 @@
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <assert.h>
#include "backend.h"
#define ARRAY_SIZE(a) (sizeof(a)/sizeof((a)[0]))
#define VER_MIN(a, b) ((a) < (b) ? (a) : (b))
extern const struct gbm_backend gbm_dri_backend;
@@ -51,15 +53,19 @@ find_backend(const char *name, int fd)
{
struct gbm_device *dev = NULL;
unsigned i;
uint32_t abi_ver;
for (i = 0; i < ARRAY_SIZE(backends); ++i) {
if (name && strcmp(backends[i].name, name))
continue;
dev = backends[i].backend->create_device(fd);
abi_ver = VER_MIN(GBM_BACKEND_ABI_VERSION,
backends[i].backend->v0.backend_version);
dev = backends[i].backend->v0.create_device(fd, abi_ver);
if (dev) {
dev->backend_desc = &backends[i];
assert(abi_ver == dev->v0.backend_version);
dev->v0.backend_desc = &backends[i];
break;
}
}
@@ -96,5 +102,5 @@ _gbm_create_device(int fd)
void
_gbm_device_destroy(struct gbm_device *gbm)
{
gbm->destroy(gbm);
gbm->v0.destroy(gbm);
}